The present invention relates to an optical device suitably applicable, for example, to a camera lens, an optical filter or the like, a lens-barrel for holding the optical device, and an image pickup apparatus and an electronic apparatus on which the optical device is mounted.
Conventionally, in image pickup devices and the like such as lens, optical filter, and CCD (Charge Coupled Device) used for cameras, debris or dust and the like deposited on the surface of the device may be actually outputted as an image, which constitutes a large proportion of the factors worsening the yield in the manufacturing process of the product. Therefore, prevention of the deposition of debris or dust has been an important problem to be solved for enhancing the yield.
As a measure against the problem, a method has been generally used in which the component parts are cleaned ultrasonically, and then the component parts are assembled into the desired product in a clean room sufficiently deprived of debris and dust. However, provision of an ultrasonic cleaning machine and a clean room for this purpose requires a huge cost, leading to an increase in the manufacturing cost and, hence, to a rise in the price of the product.
In view of the above, as a method requiring neither an ultrasonic cleaning machine nor a clean room, a method may be contemplated in which the surface of a lens or the like is provided with an antistatic effect while retaining an anti-reflection function, to thereby prevent the deposition of debris or dust which might otherwise arise from static electricity. As to the technique of providing also the antistatic effect while retaining the anti-reflection effect, a number of reports have been made in which a transparent conductive thin film is used. For example, Japanese Patent Laid-open No. Hei 2-94296 proposes a laminate film composed of a transparent dielectric film and a transparent conductive thin film, for the purpose of eliminating electrostatic charges generated on surface panels of various computer displays, CRTs of TV receivers, etc.
However, all the above-mentioned techniques are characterized in that the antistatic effect is obtained by grounding a transparent conductive thin film, and it may therefore be necessary to provide an electrode for exclusive use and to conduct a grounding treatment. Accordingly, in the case of applying the above-mentioned configuration to an optical device, for example, a lens of a camera, it may be necessary for the wiring and grounding to be carried out by taking into account a movable portion for adjusting the focus, so that it is very difficult to conduct the wiring. Further, since it may be necessary to take out the electrode for grounding the transparent conductive thin film, it may be necessary to conduct an etching treatment after the formation of the laminate film or to mask the electrode portion during the film forming step, with the result of an intricate manufacturing process.
Thus, there is a need to provide an optical device which has both an antistatic effect and an optical multi-layer effect and which is free of the need for a grounding treatment for prevention of electrostatic charging, and an image pickup apparatus and an electronic apparatus on which the optical device is mounted.
As for the level of the antistatic effect, particularly, there is a need not for eliminating the strong electrostatic charges generated on a surface panel of a TV CRT or the like, but for eliminating the weak electrostatic charges which would spontaneously attract dust and debris suspended in a natural space.